<template>
  <div class="s-canvas">
    <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
  </div>
</template>
<style>
#s-canvas{cursor: pointer}
</style>

<script>
  export default {
    name : 'SIdentify',
    props : {
      identifyCode      : { type : String, default : '1234' },
      fontSizeMin       : { type : Number, default : 16 },
      fontSizeMax       : { type : Number, default : 40 },
      backgroundColorMin: { type : Number, default : 220 },
      backgroundColorMax: { type : Number, default : 255 },
      colorMin          : { type : Number, default : 50 },
      colorMax          : { type : Number, default : 100 },
      lineColorMin      : { type : Number, default : 40 },
      lineColorMax      : { type : Number, default : 180 },
      dotColorMin       : { type : Number, default : 0 },
      dotColorMax       : { type : Number, default : 255 },
      contentWidth      : { type : Number, default : 112 },
      contentHeight     : { type : Number, default : 38 }
    },
    methods : {
      // 生成一个随机数
      randomNum(min, max) {
        return Math.floor(Math.random() * (max - min) + min)
      },
      // 生成一个随机的颜色
      randomColor(min, max) {
        let r = this.randomNum(min, max)
        let g = this.randomNum(min, max)
        let b = this.randomNum(min, max)
        return 'rgb(' + r + ',' + g + ',' + b + ')'
      },
      drawPic() {
        let canvas = document.getElementById('s-canvas')
        let ctx = canvas.getContext('2d')
        ctx.textBaseline = 'bottom'
        // 绘制背景
        ctx.fillStyle = this.randomColor(this.backgroundColorMin, this.backgroundColorMax)
        ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
        // 绘制文字
        for (let i = 0; i < this.identifyCode.length; i++) {
          this.drawText(ctx, this.identifyCode[i], i)
        }
        this.drawLine(ctx)
        this.drawDot(ctx)
      },
      drawText(ctx, txt, i) {
        ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax)
        ctx.font = this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei'
        let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
        let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
        let deg = this.randomNum(-45, 45)
        // 修改坐标原点和旋转角度
        ctx.translate(x, y)
        ctx.rotate(deg * Math.PI / 180)
        ctx.fillText(txt, 0, 0)
        // 恢复坐标原点和旋转角度
        ctx.rotate(-deg * Math.PI / 180)
        ctx.translate(-x, -y)
      },
      drawLine(ctx) {
        // 绘制干扰线
        for (let i = 0; i < 8; i++) {
          ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax)
          ctx.beginPath()
          ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
          ctx.lineTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight))
          ctx.stroke()
        }
      },
      drawDot(ctx) {
        // 绘制干扰点
        for (let i = 0; i < 100; i++) {
          ctx.fillStyle = this.randomColor(0, 255)
          ctx.beginPath()
          ctx.arc(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI)
          ctx.fill()
        }
      }
    },
    watch : {
      identifyCode() {
        this.drawPic()
      }
    },
    mounted() {
      this.drawPic()
    }
  }
</script>
